Perfluorooctyl and Perfluorobutyl Bonded Alumina Stationary Phases for High Performance Liquid Chromatography

Abstract

The preparation and properties of perfluorooctylalumina (PFOA) and perfluorobutylalumina (PFBA) high performance liquid chromatographic stationary phases have been investigated. The PFOA phase was produced by chemisorption of perfluorooctanoic acid onto the surface of alumina. The PFBA phase was produced by a similar adsorption of perfluorobutylphosphonic acid onto alumina. Both phases exhibit reverse phase liquid chromatographic properties. Elemental analyses of these materials indicated that alkyl group surface coverage of the PFBA phase is higher than that of the PFOA phase. In contrast, retention of solutes on the PFBA phase is lower than that of PFOA. Isocratic capacity factors of over 20 compounds on the PFOA and PFBA phases were determined and compared with those obtained on octadecylalumina (ODA) and octadecylsilica (ODS) phases. In contrast to the greater retention of phenols than other compounds that was evident on the unfluorinated ODA phase, the retention of phenols on the PFOA and PFBA phases was not found to be significantly different from that of other compounds. These results are attributed to a reduced degree of hydrogen bonding interactions between phenolic solutes and the PFOA and PFBA phases compared to those which occur between phenols and the ODA phase. Preliminary investigations of the utilization of the PFOA phase for the separation of peptides and the employment of the PFBA phase for the rapid separation of phenols are also described.